PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Not specified Renal: Not specified Other: No focal or generalized seizure(s) within 30 days prior to enrollment No other prior or concurrent malignancy except carcinoma in situ of the cervix or basal cell or squamous cell skin cancer No medical instability due to non-malignant systemic disease No other prior or concurrent condition that would preclude study compliance Not pregnant Fertile patients must use effective contraception